'Swab your throat first and then your nose': 4 disease experts offer new guidance on COVID-19 rapid tests
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- New research suggests Omicron may be easier to detect in saliva than nasal samples.
- Some experts recommend swabbing your throat then your nose for a COVID-19 rapid test, even if the test doesn't say to.
- The FDA and testing manufacturers advise against performing throat swabs at home.
The FDA has authorized just one method of taking a COVID-19 rapid test: swabbing the inside of your nose.
But ever since Omicron came into force in the US in mid-December, some people have noted on social media that their rapid tests only come back positive after adding saliva to the mix. The anecdotes raised questions about whether throat swabs could increase a test's accuracy, or detect virus particles before a standard nose swab.
Four disease experts told Insider they agree that it could be a good idea to throat-swab at home, even if the test doesn't call for it. But most recommended sticking the swab up your nose as well.
"If you were my friend, I would say to you, 'Yeah, I would suggest that you swab your throat first and then your nose,'" Irene Petersen, an epidemiology professor at University College London, told Insider.
If the test comes back positive, there's little reason to doubt the results, experts added. But since rapid tests were not designed to include a throat-swab, it doesn't hurt to verify the results with a lab-quality PCR test, said Susan Butler-Wu, who directs clinical testing for infectious diseases at the University of Southern California.
"I get why people are doing it," Butler-Wu said of throat swabbing. "I'd probably do it myself. But I would want to confirm if it was positive."
Throat swabs haven't been vetted by the FDA for use at home
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Test manufacturers and US health agencies aren't recommending at-home throat swabs yet.
"The FDA advises that COVID-19 tests should be used as authorized, including following their instructions for use regarding obtaining the sample for testing," an FDA spokesperson told Insider, adding: "The FDA has noted safety concerns regarding self-collection of throat swabs, as they are more complicated than nasal swabs — and if used incorrectly, can cause harm to the patient."
Abbott, one of the leading producers of rapid tests in the US, told Insider that its rapid test, BinaxNOW, should be used exclusively as a nasal swab because that's how it was designed.
"The test is highly accurate when used as intended," an Abbott spokesperson said.
Why throat swabbing may help detect a positive case
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Scientists have generally understood nasal swabs to be better at detecting respiratory viruses, including SARS-CoV2.
"The cells in the lining of the nose are much more similar to the cells deeper in the lungs," Sheldon Campbell, associate professor of laboratory medicine at Yale School of Medicine, told Insider. "That's traditionally why we've diagnosed all these viruses up in the nose."
But it's possible the Omicron variant may change the way the coronavirus replicates or congregates in the body.
In a December study that hasn't been peer reviewed, South African researchers found that saliva tests were better at picking up Omicron than nasal tests — detecting 100% of cases, while nasal swabs were only 86% sensitive. With Delta, the opposite was true: Saliva swabs were 71% sensitive, whereas nasal swabs were 100% sensitive.
On Wednesday, a team of US researchers released another small study — also not-yet-peer-reviewed — that supported those findings. They found that the viral load from an Omicron infection peaked in saliva one to two days before it peaked in nasal swabs.
The study was based on samples from just 30 people. But these new results back up what Twitter's rogue citizen scientists have suggested — that throat swabs might be detecting Omicron earlier in the course of a vaccinated person's illness than nasal swabs can.
The throat may carry a higher viral load in Omicron's case
Omicron's unique pattern of symptoms may offer more clues about where the variant prefers to hang out in the body.
Tens of thousands of Omicron patients in the UK log their symptoms every day using the Zoe COVID app, and 60% say they're suffering from a sore throat, making it one of the top five symptoms there. Many of those patients also report that sore throat is one of their earliest symptoms. Health officials in both the US and European Union are, similarly, noting fewer instances of fever or loss of taste and smell with Omicron, when compared with other variants.
"It may be that Omicron is showing us a slightly different set of symptoms, and that may reflect perhaps a change in where this virus is infecting in your respiratory tract or how well it's infecting certain cells in your respiratory tract," Andy Pekosz, a virologist at the Johns Hopkins Bloomberg School of Public Health, told Insider.
"When you hear the same anecdotes from people that say a lot of them have a scratchy throat, it is probably because that's where the highest concentration of the virus is at that point," Petersen added. The variant, she said, "may colonize the tissues in the throat earlier than in your nose."
That could, theoretically, be even more true now that "many people are vaccinated," she said, a potential early sign their vaccine-induced immunity is kicking in. "Therefore, they may develop symptoms very early on, when they still have very little viral material, especially in the nose."
On the other hand, throat swabs might simply be picking up on drainage from the nose, Campbell said.
"It's not implausible that there's a fair amount of virus in the back of the throat — even if it's not replicating there, frankly, because everything runs down there from the nose," he said.
How to perform a throat swab properly
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If you're going to try swabbing your throat at home, there are a few key things to know. Many rapid tests in the UK use a combined throat/nose swab, and the UK Health Security Agency has a brief how-to video.
First, it's important not to drink, eat, or brush your teeth for at least 30 mins prior to performing the swab, because it's possible that could mess with your test results.
"We're talking about basically putting something onto a strip of special paper," Butler-Wu said of how the rapid antigen tests work. "So we worry more about random chemical interference, potentially."
Next, always be sure to wash your hands thoroughly before testing. Then, stand in front of a mirror, and open wide.
Stick out your tongue, so you can see the bridge-like, arched surface that extends across the roof of your throat. The area directly behind that bridge, where your tonsils jut out on either side, is the place we're interested in sampling for virus. Sweep across both tonsils, at the top of the very back of the mouth, for several seconds. Avoid touching the tongue, teeth, or the insides of your cheeks with the swab.
Be gentle, but swab judiciously back and forth across both tonsils firmly, at least four times. Sampling this far back may activate your gag reflex, but it shouldn't hurt you.
Then, proceed with your nose swab as usual. It's very important to swab your throat before your nose, because you don't want to introduce anything that may be stuck in your nose down your throat.
Some experts said they expect manufacturers to come out with updated guidance for rapid tests soon, though Abbott declined to comment on whether that was the case.
"Nobody's trying to dupe anybody," Butler-Wu said. "We're all thrown into this hot mess together trying to figure it out."
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